Tissue engineering (TE) and regenerative medicine are evolving interdisciplinary fields based on both biological and engineering principles. These fields attempt to mimic the natural processes of tissue formation and regeneration (Vacanti and Lander, 1999). In a context of organ shortage, and an ever increasing number of patients on waiting lists for transplants, TE offers a viable alternative to the existing therapeutic options, as it promises to provide transplantable substitutes that restore, maintain or improve tissue function and integrity. Traumatic injury, tumor resections, degenerative disease, and congenital or acquired malformations can all require the reconstruction of adult tissue. Traditional approaches in reconstructive surgery, such as autografts, allografts or synthetic substitutes, are all inherently problematic. Autograft based therapy is limited by host morbidity and availability; allograft based therapy is limited by immune rejection and the risk of disease transmission; synthetic grafts are inferior to their biological counterparts, and have a relatively high failure rate.
TE is based on the use of cells, scaffolds and bioactive factors, such as chemical substances and mechanical stimuli. A number of cell types have already been used for TE applications, including fully matured cells derived from adult tissues, and stem cells. Stem cells can maintain and repair tissues, and can be derived from embryonic, fetal or adult sources (Lavik and Langer, 2004; Sharma and Elisseeff, 2004).
Nonetheless, several fundamental obstacles still need to be addressed when designing cell-based therapies, such as the risk of rejection of transplanted cells by the host immune system, and the risk of uncontrolled differentiation and proliferation of the transplanted cells, which can result in tumor formation.
While autologous cell-based strategies may offer a solution to immune rejection problems, patient-specific therapies raise critical questions regarding regulatory and economic issues.
It has also been shown that an extract from pluripotent cells, such as oocytes and embryonic stem cells, can manipulate gene expression and epigenetically reprogram somatic cells (Collas and Gammelsaeter 2007). In addition, the extracellular microenvironment is also known to play a significant role in modulating cell phenotype and behavior (Nelson and Bissell 2006).
U.S. Pat. No. 7,264,826 discloses pharmaceutical compositions comprising keratinocyte cell lysate and at least one antiflocculant and/or antisedimentation agent for treating skin wounds.
WO 2007/149861 discloses pharmaceutical compositions comprising stem cell products (SCP), e.g. cell fractions or cell lysates. This application also discloses a matrix combined with SCPs for administration to a patient, as well as methods of regenerating soft tissue in a patient comprising administering the stem cell compositions or the matrices.
WO 06/138718 discloses a biologically active three-dimensional scaffold which can be obtained from non-structural ECM extracts. The invention employs MATRIGEL which is a complex mixture of non-structural ECM molecules (such as collagen IV and laminin) and further contains growth factors and other biologically active molecules.
WO05/121316 discloses tissue-based scaffolds for supporting the growth, development and differentiation of cells and for supporting or effecting morphological changes to cells. The tissue material is preferably derived from muscle tissue and comprises a preparation comprising basement membrane components.